This invention relates to ice making machines and more particular to an improved self-contained ice making machine.
In the past, two types of ice making machines have existed. The first type is used in connection with household refrigerators; this type is not self-contained. In general they rely upon thermostats to sense the temperature of the ice trays; at a certain temperature, an ejection motor is turned on to rotate ice cube removal arms and timing cams for controlling operation.
The second type is the self-contained ice maker used in motels, restaurants, and stores. Principally, this type freezes a slab of ice cubes held together by an ice bridge. In this type, during the freezing cycle water is continually flowed over and recirculated over an evaporator rack to freeze first the ice cubes and then the bridge. The freezing of the ice cubes is determined from the temperature of the evaporator, after which a timer controls the bridge thickness and the freezing cycle is discontinued. At this time, a defrost cycle is begun.
The defrost cycle is initiated by turning off the condenser fan and energizing a hot gas solenoid valve. Hot gas from the compressor is allowed to flow directly to the evaporator grid to melt the ice cube slab from the grid. The ice cube slab is held to the grid by the capillary action of the melted ice; a probe driven by a slip clutch type motor overcomes the capillary attraction to push the ice cube slab into an ice bin. A cam on the probe motor signals the harvest of the ice cubes to restart the freezing cycle. An electro-mechanical type controller uses sensor actuated relays to control their operation. Before the next freezing cycle begins the remaining water, that had been circulating over the freezer plate and has a high mineral content, is removed through the overflow tube from the water tank reservoir. The tank is then refilled with water by energizing a water valve solenoid. In both types of ice making machines, the operation is controlled by an electro-mechanical type controller using sensor actuated relays to control other relays and cams, with the last described type replacing more of the cams with more reliable electrical relays.
In principle, the ice making machine according to the invention corresponds to the known ice making machine briefly described above. The essential difference is that the electro-mechanical controller has been replaced with a programmable controller, and the operation cycle has been modified to include a harvest anticipation cycle. The advantages are that the programmable controller provides a complete diagnostic capability in addition to improved manufacturing, operation and maintenance costs; the harvest anticipation feature reduces the operation cycle time to produce more ice in a given time period.